1. Field of the Invention
The present invention is related to an anti-theft security device for trailers of trucks.
It is related to the field of high tonnage road transportation undertaken by articulated heavy weight vehicles of the semi-trailer type constituted by a road tractor and a trailer capable of being detached, and its object is to prevent the theft of such trailer when it is immobilized and uncoupled.
2. Discussion of Background Information
Semi-trailers are constituted by a road tractor and a trailer equipped with a standardized coupling system, which enables any type of trailer to be attached to any tractor. Loads of all types are transported by such vehicles, and it is not rare for these loads to represent a substantial amount of money, which naturally attracts thieves.
During transport, the trailers with their load are often detached, for example, while being grouped or de-grouped, and left waiting, to enable the tractor to be attached to other trailers so as to use the equipment profitably, with the equipment being specifically designed to enable such type of operations. To this end, the front of the trailer, which is deprived of wheels and rests during transport on a platform of the tractor, is equipped with two telescopic props maneuvered by means of a simple removable crank.
Currently used props are almost all of the same model, each of them being constituted by two cross-sectional tubes sliding in one another, the lower tube bearing an articulated sole resting on the ground and being actuated by an internal screw acting on a nut affixed to such tube. The screw is driven, via a bevel gear, by virtue of a double set of serrated wheels, one of which, actuated by the removable crank, is axially mobile so as to enable actuation of two different gear reductions. These serrated wheels are housed in a case affixed to one of the props, the second only comprising a bevel gear driven by a rotary bar connecting the two props.
In order to steal the trailer and its load, one need only have a standard type of tractor and a crank to actuate the props, since the latter must be raised to enable their displacement.
For some time, thefts of trailers have increased, and up until now, no satisfactory means have been found enabling such actions to be countered, except for the use of security guards, which results in both substantial and repetitive expenditure.
GB-A-1,565,542 describes a device adapted to be mounted on the existing props of semi-trailers, and includes a simple key lock acting on a rod which gets engaged in a gear of the prop maneuvering mechanism. This type of system is generally fairly easy to break into.
EP-A-0,102,339 describes an anti-theft device for automobile trailers based on the use of articulated props actuated by an electric motor controlled by a key interrupter. Such as described, this apparatus is not applicable to semi-trailers of trucks.